study of the primary decomposition of coal by infrared

A STUDY OF THE PRIMARY DECOMPOSITION OF COAL BY INFRARED

SPECTROPHOTOMETRY AND BY CHLOROFORM EXTRACTION

Raymond Virgil Smith

A thesis submitted to the faculty of the Uni"versity of Utah in partial fulfillment of the requirements for the degree of

Master of Science

Department of Fuel Technology LIBRARY

UNIVERSITY OF UTAH

University of Utah August, 1957


SPEC TROPHOTOMETRY AND BY CHLOROFORM EXTRACTION

by

Raymond. Virgil Smith

A thesis submitted to the faculty of the University of Utah in partial fulfillment of the requirements for the degree of

Master of Science

Department of Fuel Technology

University of Utah

August, 1957

,/ LIBRARY !JNIVERSITY OF. UTAH

This Thesis for the Master of Science degree

by


has been approved by

� �� (�. � ReadeJSUi)ei'Visory Committee

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ABSTRACT

For the differential I-R technique described in this paper,

two specimens of coal were prepared for runs in the infrared double

beam spectrometer. One specimen was prepared for the coal as

received from the mine and this was placed in the reference beam.

The other sample was prepared from coal which had been heated in

a pressure tight container to the softening temperature. This was

placed in the sample beam. The differential infrared spectrometer

pattern thus obtained enables one to observe the changes in the

infrared range.

In the second phase of these tests the coal was heated to

temperatures in the plastic range and then extracted with chloroform.

The extract yield was run differentially versus the untreated coal

in the infrared spectrophotometer. These tests indicated different

band intensities than the untreated coal and also revealed some

absorbtion bands which did not occur in the original coal or in the

residue extract from the absorbtion process.

The extract yield data was also used for a kinetic study of

the coal!s primary decomposition. Activation energies thus obtained

for the solid to plastic step of the reaction appear to be of the

general order of magnitude of 20 to 30 k.cal/mole*

ii

ABSTRACT

For the differential I-R technique described in this paper"



recei ved from the mine and this was placed in the reference beam.





infrared range.


temperatures in the plastic range and. then extracted with chloroform.







the coal r s primary de compo si tion. Activation energies thus obtained


general order of magnitude of 20 to 30 k.cal/mole.

i1

Acknowledgements

The author wishes to express his thanks to Dr« George

Richard Hill, Department of Fuel Technology and Dr. Milton E.

Wadsworth for their interest and help throughout this stucty-*

This research was supported in part by a J. L. Dougan

Research Fellowship in Fuel Technology and the Atomic Energy

Commission under Contract Number AT ( 1 1 - 1 ) -82, Project Number 1«

Their interest and support was greatly appreciated*

Thanks are also expressed to the U» S* Steel Corporation,

Columbia Division who supplied the coal samples for the tests.

iii

Acknowledgements

The author wishes to express his thanks to Dro George

Richard Hill, Department of Fuel Technology and Dr. Milton E.

Wadsworth f'or their interest and help throughout this study.

This research was supported in part by a J. L. Dougan

Research Fellowship in Fuel Technology and the Atomic Energy

Commission under Contract Number AT (11-1) -82, Project Number 10

Their interest and. support was greatly appreciated.

Thanks are also expressed to the U. S. Steel Corporation,

Columbia Division who supplied the coal samples for the tests.

iii

TABLE OF CONTENTS

I. INTRODUCTION 1

II. INFRARED SPECTROPHOTOMETRY STUDY OF THE COAL HEATED TO THE PLASTIC STAGE 8

III. INFRARED SPECTROPHOTOMETRY STUDY OF THE CHLOROFORM EXTRACTION OF HEATED COALS l£

IV. KINETIC STUDY OF THE FORMATION OF A CHLOROFORM

SOLUBLE MATERIAL 19

V. CONCLUSIONS • . . • 23

VI. RECOMMENDATIONS 2$

APPENDICES. . • 26

BIBLIOGRAPHY 33

iv

TABLE OF CONTENTS

I. INTRODUCTION. • • • • 0 • • • • • • • 1

TI. INFRARED SPECTROPHOTOMETRIC STUDY OF THE COAL HEATED TO THE PLASTIC STAGE. • • • • • • 0 • 8

III. INFRARED SPECTROPHOTOMETRIC STUDY OF THE CHLOROFORM EXTRACTION OF HEATED COALS 0 • • • • 15

IV. KINETIC STUDY OF THE FORHATION OF A CHLOROFORM SOLUBLE MATERIAL • • • • • • • • • • • o 19

v. CONCLUSIONS • • • • • 0 • • • • • • • • 23

VI. RECOM}lENDATIONS. • • • • • • • • 0 • • • 25

APPENDICES. • • • • • • • • • 0 • • • 0 0 • 26

BIBLIOGRAPHY • • • • • • • • • • • • • • • • 33

iv

I. INTRODUCTION

The primary decomposition of coal is closely related to the

quality of coke the coal will ultimately produce.

Coke and Coke Quality 9

Fuels and Combustion Handbook defines coke as a "•••fused,

cellular, porus structure that remains after free moisture and the

major portion of the volatile matter have been distilled from

bituminous coal and other carbonaceous material by the application

of heat in the absence of air or in limited supply*" Chemistry of

Coal utilization10 states that about 1$% of the total annual coal

production has been coked for a number of years.

The required quality of the finished coke for blast furnace

use is very loosely defined. Fuels and Combustion Handbook^ states

"The real answer is to be had only from the blast furnace."

Chemistry of Goal Utilization adds, "The correct evaluation of

blast furnace coke is s till an unsolved problem."

Two tests which determine the strength and therefore the

acceptability of the coke are the Drop Shatter (A.S.T.M. D1U1-U8) and

Tumbler (A.S.T.M. D29U-50) Tests •

In the Shatter Test, 50 pounds of coke all over 2 inches in

size are placed in a box and dropped four times from a height of 6 1

I. INTRODUCTION

The primary d.ecomposi tion of coal is closely related to the

quality of coke the coal will ultimately produce.

Coke and Coke Qual! ty

Fuels and Combustion Handbook9 defines coke as a n •• ofused,

cellular" porus structure that remains after free moisture and the

major portion of the volatile matter have been distilled from

bituminous coal and other carbonaceous material by the application

of heat in the absence of air or in limited supply." Chemistr,r of

Coal utilizationlO states that about 15% of the total annual coal

production has been coked for a number of years.

The required quality of the finished coke for blast furnace

use is very loosely defined. Fuels and. Combustion Handbook9 states

"The real answer is to be had only from the blast furnace."

Chemistry of Coal Utilization adds, "The correct evaluation of

blast i'urnace coke is s till an unsolved problem."

Two tests which determine the strength and therefore the

acceptability of the coke are the Drop Shatter (A.S.T.M. D14l-48) and

Tumbler (A.S.T.M. D294-50) fests •

In the Shatter Test, 50 pounds of coke allover 2 inches in

size are placed in a box and dropped four times from a height of 6

1

2

feet on a steel plate. The resulting product is sieved on 2, if, and

1 inch screens. The Shatter Index is the amount remaining on a

given size screen.

In the Tumbler Tests coke is placed in a drum and rotated

at a specified speed for a fixed length of time. There is statis

tical correlation between coke quality and the Shatter and Drum Tests©

The size as well as the strength of the coke is an important

factor in the blast furnace. A uniform size of coke seems to produce

the greatest void value and the best ratio of coke consumption per

ton of iron produced.

There are many other tests for coke quality which include

determinations of reactivity, density, combustability, absorbtivity,

electrical conductivity and compression strength.

Tests to Determine Coking Quality

Determination of the rank of the coal proves to be a rough

measure of the coal's coking quality. In general, the low volatile,

bituminous coal produces the best coke. Most papers in this search

indicate that coal with a carbon content in the Q0% to 90% range

produce the best coke.

Chemistry of Coal Utilization3*0 lists nine types of tests to

determine the coking quality. Those most often referred to in the

literature are the Free Swelling, (A.S.T.M. D?20-l;6) Giesler

Plastometer and Dilatometer Tests*

Two types of Free Swelling Tests are Agglutinating and Agglomerating. In the Agglutenating Test, one gram of coal with

2

feet on a steel plate. The resulting product is sie-ved on 2, Ii, and

1 inch screens. The Shatter Index is the amount remaining on a

given size screen.

In the Tumbler Tests coke is placed in a drum and rotated

at a specified speed for a fixed length of time. There is statis

tical correlation between coke quality and the Shatter and Drum Tests.

The size as well as the strength of the coke is an important

factor in the blast .furnace 0 A uniform size of coke seems to produce

the greatest void value and the best ratio of coke consumption per

ton of iron produced.

There are many other tests for coke quality which include

determinations of reactivity, density, combustability, absorbtivity"

electrical conductivity and compression strength.

Tests to Determine Cokin;; Quality

Determination of the rank of the coal proves to be a rough

mea'5Ure of the coal's coking quality. In gereral" the low volatile,

bituminous coal produces the best coke. Most papers in this search

indicate that coal with a carbon content in the 80% to 90% range

produce the best coke.

Chemistry of Coal UtilizationlO lists nine types of tests to

determine the coking quality. Those most often referred to in the

literature are the Free Swelling, (A.S.T.M. D720-46) Giesler

Plastameter and Dilatometer Tests.

Two types of Free Swelling Tests are Agglutinating and

Agglomerating. In the Agglutenating Test, one gram of coal with

3

varying amounts of inert material is carbonized at 950 degrees C. The

recorded results are the maximum weight of inert material per gram

of coal that will produce a coke button which will sustain a 5>00 g.

weight without crushing. In the Agglomerating Test, one gram of

coal is heated at 9^0 degrees C. The tendency to swell and the

ability to support a $00 g© weight are observed.

The Dilatometer testing method uses a piston on the coal,

free to move as the coal swells on heating. The vertical displacement

of the piston is recorded.

In the Giesler Plastometer Test a constant torque is applied

on wire-like fingers in the coal throughout a temperature programmed

heating process. Dial divisions of rotation of the torqued fingers

in the coal are recorded versus temperature.

Data and Theories on the Coking Mechanism

The key to coking seems to be in the fluid behavior of the

coal as it is heated. This pointed up by the Free Swelling and

Plastometer Tests and, more recently, by the work of Dryden and

Panchurst.1 They discovered that a chloroform soluble product is

formed near the softening temperature. They proved that this ex

tracted portion was an important part of the plastic stage by three

tests. In the first test a coking coal would not swell on heating

after the extracted portion had been removed. Attempts to extract

material from a non-coking coal did not result in a good yield of

soluble product and the yield did not rise as the softening

3

varying amounts of inert material :i,.s carbonized at 950 degrees C. The

recorded results are the maximum weight of inert material per gram

of coal that will produce a coke button which will sustain a 500 g.

weight without crushing. In the Agglomerating Test, one gram of

coal is heated at 950 degrees C. The tendency to swell and the

ability to support a 500 go rleight are observed.

The DilatOllleter testing method uses a piston on the coal,

free to move as the coal swells on heating. The vertical displacement

of the piston is recorded.

In the Giesler Plastometer Test a constant torque is applied

on wire-like fingers in the coal throughout a temperature programmed

heating process. Dial divisions of rotation of the torqued fingers

in the coal are recorded versus temperature.

Data and Theories on the Coking Mechanism.

The key to coking seems to be in the fluid behavior of the

coal as it is heated. This pointed up by the Free Swelling and

Plastometer Tests and, more recently, by the WOrk of Dryden and

Panchurst. l They discovered that a chloroform soluble product is

fonned near the softening temperature. They proved that this ex

tracted portion was an important part of the plastic 'stage by three

tests. In the first test a coldng coal would not swell on heating

after the extracted portion had been removed. Attempts to extract

material from a non-coking coal did not result in a good yield of

soluble product and the yield did not rise as the softening

temperatures were reached as it did in the coking coal* In the

third tests, adding the extract yield to a non-coking coal produced

softening and swelling properties in it which it did not possess

prior to the addition* Further tests on the extracted portion

indicated that the extract was more fluid on heating than the origi

nal coal* They found that the extract contained more hydrogen and

less oxygen than the original coal* They also stated that an

infrared spectra showed that both the extract and the residue

resembled the original coal* The yield of extract was found to

drop off rather sharply if softening temperatures were held for

longer periods of time during t&e heating process*

There is a good deal of infrared spectrophotometry data on

coal* Some of the points brought out by previous studies follow •

1* Four papers^' 6* 7* 1 1 all report heavy OH bands (2.7 to 3*1

microns) in high volatile matter, poor coking coal* This bond disap

pears on heating. In general, this bond does not appear in the

spectra of higher ranked coals which have good coking characteristics* 2 7 11 12

Several papers >*> ' all suggest that the low rank, high volatile

matter coal!s inability to coke is because of the strong linkages of

these OH groups* J. K. Brown^ however, states "The simple explanation

that strong intermolecular forces associated with hydrogen-bonding

restricted the ability of the weakly coking coal to become plastic

and swell is not satisfactory and is not in accord with a number of

facts known about the coking process (e.g* the destruction of coking

power by solvent extraction)*11

4

temperatures were reached as it did in the coking coal. In the

third tests, adding the extract yield to a non-coking coal produced

softening and swelling properties in it which it did not possess

prior to the addition. Further tests on the extracted portion

indicated that the extract was more fluid on heating than the origi

nal coal. They found that the extract contained more hydrogen and

less o:xygen than the original coal. They also stated that an

infrared spectra showed that both the extract and the residue

resembled the original coal. The yield of extract was found to

drop off rather sharply if softening temperatures were held for

longer periods of time during the heating process.

There is a good deal of infrared spectrophotometr;ic data on

coal. Some of the points brought out by previous studies follow •

1. Four papers~,6,7,ll a1l report heavy OH bands (2.7 to 3.1

microns) in high volatile matter, poor coking coal. This 'bond disap

pears on heating. In general, this bond does not appear in the

spectra of higher ranked coals which have good coting characteristics.

Several papers2,7,ll,12 all suggest that the low rank, high volatile

matter coalts inability to coke is because of the strong linkages of

these OH groups. J. K. Pirmm6 however, states "The simple explanation

that strong intermolecular forces associated with hydrogen-bonding

restricted the ability of the weakly coking coal to become plastic

and swell is not satisfactory and is not in accord with a nUlllber of

facts known about the coking process (eg. the destruction of coking

power by solvent extraction)."

2* H. H. Storch indicates weathered and oxidized coals

show a strong carbonyl (5*87 microns) band absorption. Kinkby,

Lakey, and Sareant1^ find this a strong absorption band in low rank

coals*

3* There is some confusion on the 6*19 micron band* H* H.

Storch points out that it is hard to separate from the hydrogen

bonded OH at 6*1 microns and 6*20 microns* He concludes, however

that the absorption at 6.19 microns is a result of phenoxyl or

quinoidal compounds* J. K. Brown^ found the 6*19 micron absorption

in all coals except anthracite. ?He identified the band with an

aromatic ring frequency or with a carbonyl group* He does not

believe this absorption indicates a phenolic group because the

intensity of the absorption does not decrease with the carbon content

in the coal.

lu Three papers^'7*11 report a rather strong absorption in

the 8 micron region. Two of these authors^'11 state this is the

result of aromatic oxygenated compounds* One of the papers suggests

that this absorption indicates the presence of polycyclic quinone

compounds. They find this absorption band quite stable for coal

ranks 78$ to 89$ carbon*

5* Fridel and Queiser^ report that kstolinite or an aromatic

ether represent the 9*67 micron absorption band*

6. Several papers report that high background absorption

increases with the rank of the coal and this background may be

5

20 H. H. Storchll indicates weathered and oxidized coals

show a strong carbonyl (5.87 microns) band absorption. Kinkby,

Lakey I and Sareantl6 find this a strong absorption band in low rank

coals.

3. There is some confUsion on the 6.19 micron band. H. H.

storch points out that it is hard to separate from the hydrogen

bonded OH at 6.1 microns and 6.20 microns. He concludes, however

that the absorption at 6.19 microns is a result of phenoxy1 or

quinoida1 compounds. J. K. Brown6 found the 6.19 micron absorption

in all coals except anthracite. '?He identified the band with an

aromatic ring frequency or with a carbonyl group. He does not

believe this absorption indicates a phenolic group because the

intensity of the absorption does not decrease with the carbon content

in the coal.

4. Three papers6,7,llreport a rather strong absorption in

the 8 micron region. Two of these authors6,ll state this is the

result of aromatic oxygenated compoundso One of the papers suggests

that this absorption indicates the presence of polycyclic quinone

compounds. They find this absorption band quite stable for coal

ranks 78% to 89% carbon.

541 Fridel and Queiser5 report that kaolinite or an aromatic

ether represent the 9.67 micron absorption band.

6. Several papers report that high background absorption

increases with the rank of the coal and this background may be

6

caused by pi electrons^ in condensed aromatic rings or by scattering.7

J. Ko Brown^ used infrared spectrophotometry to study a

weakly caking coal and a coking coal heated to various temperatures.

As a result of this study he suggested that the removal of the

aliphatic hydrocarbons leaves unsatisfied edge valences which are

satisfied by C-C cross links. This reaction, he believes, continues

above degrees C. (above which the high background opaqued his

spectra) with a further loss of hydrogen from the ring systems. 7

Brown and Hirsch' found by use of X-Ray diffraction techniques

that the number of condensed aromatic rings goes up rapidly for

coals with about 87$ carbon content. They report that 1$% of the

carbon in a coal containing a total of 85$ carbon is in condensed

aromatic rings.

A. Whitacker"""̂ using the data produced by the X-Ray technique,

studied the fringe groups -which satisfy the edge valences of the

carbon rings. From the amount of unorganized material and from his

computed number of edge valences he concluded that there is barely

enough unorganized material to go around to satisfy the edge valences

unless there are considerable direct linkages. His work indicates

that fringe structures, for the most part, must be composed of

rather simple groups.

Fitzgerald1^ made a kinetic study of the plastic zone

reaction, evaluating the reaction velocity from the Giesler Plasto-

meter data. He points up the fact that fluidity is a function of

6

caused by pi electrons5 in condensed aromatic rings or by scattering.7

J. Ko F5rawn6 used infrared spectrophotometry to study a

weakly caking coal and a coking coal heated to various temperatures.

As a result of tlUs study' he suggested that the removal of the

aliphatic hydrocarbons leaves unsatisfied edge valences which are

satisfied by C-C cross links. This reaction, he believes, continues

above 550 degrees C. (above which the high background opaqued his

spectra) with a further loss of hydrogen from the ring systems.

Brown and Hirsch 7 found by use of X-Ray diffraction techniques

that the number of condensed aromatic rings goes up rapidly for

coals with about 87% carbon content. They report that 75% of the

carbon in a coal containjng a total of 85% carbon is in condensed

aromatic rings.

A. 'Whitacker12 using the data produced by the X-Ray technique,

studied the fringe groups which satisfy the edge valences of the

carbon rings. From. the amount of unorganized material and from his

computed number of edge valences he concluded that there is barely

enough unorganized material to go around to satisfy the edge valences

unless there are considerable direct linkages. His work indicates

that fringe structures, for the most part, must be composed of

rather simple groups.

Fitzgerald13 made a kinetic study of the plastic zone

reaction, evaluating the reaction velocity from the Giesler Plasto

meter data. He points up the fact that fluidity is a function of

7

both temperature and time because at a constant temperature the

fluidity goes to a maximum and then falls off. He observed that

this indicates a decomposition reaction, first to a fluid, and then

a decomposition of the fluid to solid and volatile products* He

used the Arrhenius rate equation and found the activation energy

for several coals to be 5>0 k. cal/mole© He found a reasonably

good correlation between reaction velocity and the lj inch Shatter

Index, and suggested that the use of maximum fluidity with the

reaction velocity should produce better resultso 7 11

Two authors'>^ comment that the strength of the coal

(Young!s Modulus, grindability, hardness, and viscosity) are at a

minimum in the good coking coalsc

7

both temperature and time because at a constant temperature the

fluidity goes to a max:ilmlm and. then fa1ls of:!. He observed that

this indicates a decomposition reaction, first to a fluid, and then

a decomposition of the fluid to solid and volatile products. He

used the Arrhenius rate equation and found the activation energy

for several coals to be 50 k. cal/moleo He found a reasonably

good correlation between reaction velocity and the It inch Shatter

:Index, and suggested that the use of maximum fluidity with the

reaction velocity should produce better resultso

Two authors7,ll comment that the strength of the coal

(Young's Modulus, grindability, hardness, and viscosity) are at a

minimum in the good coking eoalso

II. INFRARED SPECTROPHOTOMETRY STUDY OF COAL HEATED TO THE PLASTIC STAGE

Procedure in the Preparation of Samples

Coal specimens were prepared for evaluation by means of

infrared spectrophotometry. The samples were ground to a very fine

powder and then thoroughly mixed in carefully weighed proportions

with potassium iodide (usually 6mg. of coal per gram of KI)« A measured

quantity of this mixture was then pressed in an evacuated die into

plates for examination. The reliability of this technique has been 2 Q h

well established in other systems.'-^'^ Infrared specta were

obtained using a Perkin Elmer Model 21 double beam recording

spectrophotometer.

In the first tests the infrared absorbtion spectrum was

obtained for three coals with a high fluidity (Giesler Plastometer

dial divisions greater than 100) and for three coals with poor fluid

properties (Geisler Plastometer dial divisions less than three).

Most of the spectral assignments have been made in previous studies.

Table II lists the spectral assignments used in this study.

Discussion of Results

For the 2*7 to 3*10 micron band the non-fluid coals showed

stronger absorbtion indicating more OH groups in these coals* This

8

110 INFRARED SPECTROPHOTOMETRIC STUDY OF COAL

HEATED TO THE PLASTIC STAGE

Procedure in the Preparation of Samples

Coal specimens were prepared for evaluation by' means of

infrared spectrophotometry. The samples were ground to a very fine

powder and then thoroughly mixed in carefully weighed proportions

with potassium iodide (usually" 6mg. of coal per gram of KI)o A measured

quantity of this mixture was then pressed in an evacuated die into

plates for examination. The reliability of this technique has been

well established in other systems?,3,4 Inf'rared specta were

obtained using a Perkin Elmer Model 21 double beam recording

spectrophotometer.

In the first tests the infrared absorbtion spectrum was

obtained for three coals with a high fluidity (Giesler Plastometer

dial divisions greater than 100) and for three coals with poor fluid

properties (Geisler Plastometer dial divisions less than three).

Most of the spectral assignments have been made in previOUS studies.



For the 2.7 to 3.10 micron band the non-fluid coals showed

stronger absorbtion indicating more OH groups in these coalso This

8

9

was in agreement with the findings of previous investigatorsJ>*^'t*^m

Two of the fluid coals showed some carbonyl bonds (5*87 microns)*

None of the other coals absorbed in this region* All of the coals

absorbed strongly at the 6*19 micron band again in agreement with

the previous investigations^ In the 8*0 micron region all coals

showed weak absorbtion* None of the coals tested absorbed at the

9*05> micron ether band* The fluid coals indicated some absorbtion

in the 9*67 micron ether region* This study was limited to the

shorter wave lengths* and the more specifically assigned bands*

The results of this series of tests indicated that the

spectra of the coals of the Rocky Mountain Region are similar to the

spectra of the coals of the other parts of the world* The spectra

also point up the fact that while some indication of a coal!s fluid

properties may be obtained from the infrared pattern, these data

are not sufficient to evaluate the fluid properties of the coal*

Procedure for Differential I-R Examination of Heated Coal

The coal used for the second tests in this series was a

blending coal used in coke ovens* The physical properties of this

coal are shown in Table I. One sample was prepared from the coal as

received from the mine* The other sample of coal was heated in a

pressure tight container to the fluid ranger this required approximately

20 minutes* The temperature in the fluid range was held for periods

9

was in agreement with the findings of previous investigators.5,6,7,l1

Two of the fluid coals showed some carbonyl bonds (5.87 microns).

None of the other coals absor1Ded in this region. All of the coals

absorbed strongly at the 6.19 micron band again in agreement with

the previous investigations. In the 8.0 micron region all coals

showed weak absorbtion. None of the coals tested absorbed at the

9.05 micron ether band. The fluid coals indicated some absorbtion

in the 9.67 micron ether region. This study was limited to the

shorter wave lengths, and the more specifically assigned bands.

The results of this series orliests indicated that the

spectra of the coals of the Rocky Mountain Region are similar to the

spectra of the coals of the other parts of the world. The spectra

also point up the fact that while some indication of a coal I s fluid

properties may be obtained from the infrared pattern, these data

are not sufficient to evaluate the fluid properties of the coal.

Procedure for Differential I-R Examination

of Rea ted Coal

The coal used for the second. tests in this series was a

blending coal used in coke ovens. The physical properties of this

coal are shown in Table I. One sample was prepared from the coal as

received from the mine. The other sample of coal was heated in a

pressure tight container to the fluid range: this required approximately

20 minutes. The temperature in the fluid range was held for periods

10

Table 1. Physical Properties of Coal Used in Differential Infrared Spectrophotometer Tests

Proximate Analysis Ultimate Analysis Gieseler Type Plastometer

H 20 C 75o20 Initial Soften. Temp. 3Ul°C

V.- M. 30.53 % &23 Max. Fluidity Temp. U22°C

F. C 58.17 N 2 1.63 Max. Dial Div./Min. 2,977

Ash r u 3 0 Ash 11*30 Solidification Temp. U69°C

Sulfur 0.82 S 0.82

°2 5o82

Table II. Spectral Assignments for Coal

Microns

2.7U - 2.78 Free OH stretching 2.82 - 3 .10 OH stretching, intermolecular hydrogen bonds 3.30 Aromatic CH, weak 3.1|.2 - 3«U9 Naphthenic and/or aliphatic CH bonds 5*87 C==°=0 band, weak shoulder 6.19 Very intense band; may be partly caused by a con

jugated carbonyl structure such as in quinones 6.90 CH2 groups 7.25 CH- groups 9.05 Ether band 9.67 Aromatic band, intense in aromatic ethers

10

Table 1. Physical Properties of Coal Used in Differential Infrared Spectrophotometer Tests

Proxima te Analysis Ul tima te Analysis Gieseler TYPe P1astometer

H2O 2094 C 75020 Ini tial Soften. Temp. 341°c

V. M. 30.53 ~ $.23 Max. Fluidity Temp. 422°C

F. C. 58.17 N2 1063 Max. Dial Div./Min. 2,977

Ash 11.30 Ash 11.30 Solidification Temp. 469°C

Sulfur 0.62 S 0.82

O2 5 0 82

Table II. Spectral Assigmnents for Coal

Microns

2.74 - 2.78 2.82 - 3.10 3.30 3.42 - 3.49 5.87 6.19

6.90 7.25 9.05 9.67

Free OH stretching OH stretc~ng, intermolecular hydrogen bonds Aromatic CH, weak Naphthenic and/or aliphatic CH bonds C-==O band, weak shoulder Very intense band; may be partly caused by a conjugated carborw1 structure such as in quinones CH2 groups CH":\ groups Etlier band Aromatic band, intense in aromatic ethers

1 1

of time from 10 to 30 minutes with all time lengths producing the

same general spectra. The sample was then quenched and prepared

as previously described.

The plate containing the untreated coal was placed in the

reference beam of the spectrophotometer and the plate containing

the coal which had been heated was placed in the sample beam. A

differential absorption spectra was thus obtained.

To prove the reliability of the differential spectrophotometer

method, two samples of untreated coal were prepared and one was

placed in the reference beam and the other placed in the sample

beams. The pattern obtained is shown in Figure 2 . The virtual

absence of absorption maxima substantiated the reliability of the

differential technique and the data obtained from it.

Discussion of the Results of the

Heated Coal Series

Figure 1 shows a typical spectrum obtained by the differential

technique. Since the coal sample which had been heated was placed

in the sample beam, peaks downward on the pattern indicated vibrational

spectra for bonds greater in number in the heated coal and peaks

upward indicated the presence of a greater number of bonds in the

untreated coal sample. Increases were noted in the 2.7 to 3*10

(OH stretching) micron range, 3»3 "bo 3«U micron (aromatic hydrocarbon),

7.2^ micron (hydrocarbon bending, CE,) and 9#67 micron (aromatic ethers).

11

of time from 10 to 30 minutes with all time lengths producing the

same general spectra. The sample was then quenched and prepared

as previously described.

The plate containing the untreated coal was placed in the

reference beam of the spectrophotometer and the plate containing

the coal which had been heated was placed in the sample beam. A

differential absorption spectra was thus obtained.

To prove the reliability of the differential spectrophotometer

method, two samples of untreated coal were prepared and one was

placed in the reference beam and the other placed in the sample

beams. The pattern obtained is shown in Figure 2. The virtual

absence of absorption maxima substantiated the reliability of the

differential technique and the data obtained from it.

Discussion of the Results of the

Rea ted Coal Series

Figure 1 shows a typical spectrum obtained by the differential

technique. Since the coal sample which had been heated was placed

in the sample beam, peaks downward on the pattern indicated vibrational

spectra for bonds greater in number in the heated coal and peaks


untreated coal sample. Increases were noted in the 2.7 to 3.10

(OR stretching) micron range, 3.3 to 3.4 micron (aromatic hydrocarbon),

7.25 micron (hydrocarbon bending, CH3 ) and 9.67 micron (aromatic ethers).

12

,—OH + H0-

\ / Other studies show that coal is primarily composed of condensed

aromatic rings. Experimental work discussed later in this paper and by

others^ indicates that the final coke satisfies these edge valences with

C - C linkages. This suggested mechanism is based on the theory that

heating coal is a continuous change of edge groups and edge bonds of

these rings. Some hydrogen would of course be available from the

decomposition of the CH groups. An aromatic ether could be a fluid in

the softening temperature range. The action of this fluid could provide

greater mobility for the rings which, in turn, may result in a better,

final orientation of the crystallites. This action would make a greater

number of C - C bonds and consequently a stronger coke.

The increases in the aromatic (3.3 micron - 3»U micron) bond

substantiates the general theories of the coking mechanism which

suggest changes to the aromatic and ultimately to a graphitic structure.

There does not seem to be any ready explanation for the increase in the

CH3 band. This, too, may represent a change in edge groups. The CH2

band shows a decrease. The £.87 micron (CO) and the 6.19 micron

(C«0-quininoid) bands are shown to increase; however, some of the tests

indicated a decrease. It would seem most probably that the 0*0 band

does decrease, however the possibilities of HgO also contributing to

one of these bands (6,19 micron) and of possible oxidation of the

The increases in aromatic ether bonds suggest the following mechanism,

^ \ - 0 - / H

12

The increases in aromatic ether bonds suggest the following mechanism.

+ HO-( \

Other studies show that coal is primarily composed of condensed

aromatic rings. Experimental work discussed later in this paper and by

others8 indicates that the final coke satisfies these edge valences with

C - C linkages. This suggested mechanism is based on the theory that

heating coal is a continuous change of edge groups and edge bonds of

these rings. Some hydrogen would of course be available fram the

decomposition of the CH groups. An aromatic ether could be a fluid in

the softening temperature range. The action of this fluid could provide

greater mobility for the rings which" in turn" may result in a better"

final orientation of the crystallites. This action would make a greater

number of C - C bonds and consequently a stronger coke.

The increases in the aromatic (3.3 micron - 3.4 micron) bond

substantiates the general theories of the coking mechanism which

suggest changes to the aromatic and ultimately to a graphitic structure.

There does not seem to be any ready explanation for the increase in the

CH3 band. This, too, may represent a change in edge groups. The CH2

band shows a decrease. The 5.87 micron (C=o) and the 6.19 micron

(C=O-quininoid) bands are sholm. to increase; however, some of the tests

indicated a decrease. It would seem most probably that the C=O band

does decrease" however the possibilities of H20 also contributing to

one of these bAnds (6.19 micron) and of possible oxidation of the

13

sample after removal from the container seems the best explanation

for the behavior of these bands© No attempt was made to interpret

bands of wave lengths greater than 9#67 micron except to note their

general increase, again substantiating the polymerization-graphiti-

zation theory©

I-R Spectra Examination of Coal Heated in a Closed Crucible

Other tests were run in a closed crucible, heated rather

quickly to temperatures in the fluid range. Samples were prepared

as before and were run against a blank of KE in the reference beam.

Figure 3 shows the results of these tests© Here the general decrease

in the bands assigned to typical edge groups is noted. One should

call attention, however, to the tendency for the OH and aromatic ether

groups to increase before finally decreasing at the higher temperatures©

The two techniques differ, of course, in that in the second

method the decomposition materials are allowed to escape© It is felt

that the first (pressure-tight container) method is a more powerful

tool for the study of the softening stage because it provides a means

for examining the bonds as they occurred in that stage before subsequent

decomposition©

X-Ray and I-R Examination of the Char

Although the char resulting from Free Swelling tests when

prepared for examination by infrared spectrophotometry produced a high

13

sample after removal from the container seems the be st explanation

for the behavior of these bands o No attempt was made to interpret

bands of wave lengths greater than 9.67 micron except to note their

general increase, again substantiating the polymerization-graphiti

zation theory.

I-R Spectra Examination of Coal Heated

in a Closed Crucible

other tests were run in a closed crucible, heated rather

quickly to temperatures in the fluid range. Samples were prepared

as before and were run against a blank of lIT in the reference beam.

Figure 3 shows the results of these tests. Here the general decrease

in the bands assigned to typical edge groups is noted. One should

call attention, however, to the tendency for the OH and aromatic ether

groups to increase before finally decreasing at the higher temperatureso

The two techniques differ, of course, in that in the second

method the decomposition materials are allowed to escape. It is felt

that the first (pressure-tight container) method is a more powerful

tool for the study of the softening stage because it provides a means

for examining the bonds as they occurred in that stage before subsequent

d.ecomposi tion.

X-Ray and I-R Examination of the Char

Although the char resulting from Free Swelling tests when

prepared for examination by infrared spectrophotometry produced a high

1U

background in the infrared absorbtion region, one sample was prepared

and successfully run using 3 rag* of coal per sample. The response was

good throught the range of frequencies. The absorbtion pattern

obtained from this test showed no absorbtion peaks* indicating a final

graphitic structure with C-C bonds.

The belief that coke is of a graphitic structure was sub

stantiated by powdering the char obtained from the coke buttons and

examining the sample by means of X-Ray diffraction. The coke button

powders showed the same general X-Ray reinforcement peaks as graphite.

These X-Ray diffraction patterns were also used to calculate the

crystallite size. These calculations showed the crystallite size for

the fluid coal to be approximately 1*5 times greater than that for

the non-fluid coal.

background in the infrared absorbtion region, one sample was prepared

and success.ful1y run using 3 mg. of coal per sample. The response was

good throught the range of frequencies. The absorbtion pattern

obtained from this test showed no absorbtion peaks,indicating a final

graphitic structure with C-C bonds.

The belief that coke is of a graphitic structure was sub

stantiated by powdering the char obtained from the coke buttons and

examining the sample by means of X-Ray diffraction. The coke button

powders showed the same general X-Ray reinforcement peaks as graphite.

These X-Ray diffraction patterns were also used to calculate the

crystallite si~e. These calculations showed the crystallite size for

the fluid coal to be approxima. te1y 1.5 time s greater than that for

the non-fluid coal.

III. INFRARED SPECTROPHOTOMETRY STUDY OF THE

CHLOROFORM EXTRACTION OF HEATED COALS

Procedure

The coal used Tor these tests was again a blending coal used

in coke ovens* Some physical properties of this coal are shown in

Table I. The coal was heated in a pressure tight container to a

temperature of 370°C in approximately 25 minutes with a period of

10 minutes at the final temperature. The sample was quenched and then

extracted in a soxhlet apparatus with chloroform. The chloroform

was then allowed to evaporate at room temperature leaving the extract

yield. This procedure was similar to that of Dryden and Panchurst

except that in these tests a pressure tight container was used as

opposed to the unsealed quartz container used by Dryden and Panchurst0

It was felt that by using the closed, higher pressure system, a more

plastic state would result and that this state would remain for a

longer period of time during heating.

Coal specimens were prepared for evaluation by means of infra

red spectrophotometry by the technique described in previous tests.

Infrared spectra were obtained using a Perkin Elmer Model 21 double

beam recording spectrophotometer. Differential spectra were obtained

by placing one sample in the reference beam and another specimen in

the sample beam. As in the previous differential tests, peaks

15

III. INFRARED SPECTROPHOTOMETRIC STUDY OF THE

CHLOROFORM EXTRACTION OF HEATED COALS

Procedure

The coal used ror these tests was again a blending coal used

in coke ovens. Some physical properties of this coal are shown in

Table I. The coal was heated in a pressure tight container to a

temperature of 3700 C in approximately 25 minutes with a period of

10 minutes at the final temperature.. The sample was quenched and then

extracted in a soxhlet apparatus with chloroform. The chloroform

was then allowed to evaporate at room temperature leaving the extract

yield. This procedure was similar to that of Dryden and Panchurst

except that in these tests a pressure tight container was used as

opposed to the unsealed quartz container used by Dryden and Panchursto

It was felt that by using the closedJ higher pressure systemJ a more

plastic state would result and that this state would remain for a

longer period of time during heating.

Coal specimens were prepared for evaluation by means of infra

red spectrophotometry by the technique described in previous tests.

Infrared spectra were obtained using a Pertin Elmer Model 21 double

beam recording spectrophotometer. Differential spectra were obtained

by placing one sample in the reference beam and another specimen in

the sample beam. As in the previous dirferential tests" peaks

15

16

downward on the pattern indicated vibrational spectra for bonds

greater in number in the specimen in the sample beam, and peaks


sample in the reference beam, Figures U,f?,6, and 7 show some of

the spectra obtained from these tests.

Discussion of the Spectra


The spectra obtained for the extract residue Figure h is similar to

the spectra of the untreated coal, Figure 1*

1* The differential spectra of Figure 3 shows in the OH

stretching region the extract contains less free OH and more inter-

molecular hydrogen-bonded OH than the untreated coalc

2 . Absorption in the 3©3 micron and 3»U2-3»li9 micron hydrocarbon

bands shows greater quantities of this material in the extract.

3 . In the 5.87 micron and 6.19 micron carbonyl region, the

5.87 band shows an increase in the extract. The 6.19 band shows a

rather indefinite change with the suggestion of some new bands in

that region. The apparent bands at 6.03 and 6.20 microns probably

result from absorption by OH bonds.

lw The 6.90 micron and the 7*2$ micron bands (CH2 and CH^)

show greater strength in the extract as would be expected from the

3.3 micron and 3«U2-3«29 micron bands and from previous work^ which

show that the extract contains more hydrogen than the untreated coal©

16

downward on the pattern indicated vibrational spectra for bonds

greater in number in the specimen in the sample beam, and peaks


sample in the reference beam. Figures 4,5,6, and 7 show some of

the spectra obtained from these tests.

Discussion of the Spectra


The spectra obtained for the extract residue Figure 4 is similar to

the spectra of the untreated coal, Figure 1.

1. The differential spectra of Figure 3 shows in the OR

stretching region the extract contains less free OH and more inter

molecular hydrogen-bonded OR than the untreated coal.

2. Absorption in the 3.3 micron and 3.42-3.49 micron hydrocarbon

bands shows greater quantities of this material in the extract.

3. In the 5.87 micron and 6.19 micron carbonyl region, the

5.87 band shows an increase in the extract. The 6.19 band shows a

rather indefinite change with the suggestion of some new bands in

that region. The apparent bands at 6.03 and 6.20 microns probably

result from absorption by OR bonds.

4. The 6.90 micron and the 7.25 micron bands (CH2 and CR3)

show greater strength in the extract as would be expected from the

3.3 micron and 3.42-3.29 micron bands and from previous workl which

show that the extract contains more hydrogen than the untreated coal.

17 5* The 9.05 micron and 9*67 micron ether bands indicate

the extract contains more of the 9•Of? vibrational absorption bands

and less of the 9*67 micron bands.

6. The extract also absorbs at four frequencies for which

there is no absorption in the untreated coal or in the residue.

These bands are at 6.6, 7*k3? &»h79 and 10.55 microns.

The 6.6 micron region most probably represents an aromatic

structure created by the softening reaction. The 7»U3 micron band

may represent an OH group for which there have been indications

in the 3 micron and 6.19 micron region. In terms of what has been

previously observed, perhaps CH^OH would be the most probable

identification for this band. A PhCHO compound could account for

the absorption in the 8.U7 and 19©55 micron wave lengths.

Taking a broad look at the extraction patterns there are

many indications of reactions of increases in the molecular OH

groups, and in the ether groups. This could be explained by a

reaction in which OH groups satisfy an edge group valence early in the

reaction finally yielding to the single bonded oxygen of the ether

group with H2O leaving the system.

It may also be noted that most of the bands are increased in

intensity in the extract. It seems reasonable to assume these bands

are for the most part edge groups on carbon ring structures. This

would indicate the extract and, in turn, the fluid portion contain

more of these edge groups. This suggests that the extract, probably

17

5. The 9.05 micron and 9.67 micron ether bands indicate

the extract contains more of the 9.05 vibrational absorption bands

and less of the.9.67 micron bands.

6. The extract also absorbs at four frequencies for which

there is no absorption in the 1.Ultreated coal or in the residue.

These bands are at 6.6, 7.43, 8.47, and 10.55 microns.

The 6.6 micron region most probably represents an aromatic

structure created by the softening reaction. The 7.43 micron band

may represent an OR group for which there have been indications

in the 3 micron and 6.19 micron region. In terms of what has been

previously observed, perhaps CH20R would be the most probable

identification for this band. A PhCHO compound could account for

the absorption in the 8.47 and 19.55 micron wave lengthso

Taking a broad look at the extraction patterns there are

many indications of reactions of increases in the molecular OR

groups, and in the ether groups. This could be explained by a

reaction in which OR groups satis~ an edge group valence early in the

reaction finally yielding to the single bonded oxygen of the ether

group with R20 leaving the system.

It may also be noted that most of the bands are increased in

intensity in the extract. It seems reasonable to assume these bands

are for the most part edge groups on carbon ring structures. This

would indicate the extract and, in turn, the fluid portion contain

more of these edge groups. This suggests that the extract, probably

18

the more significant portion of the plastic component,contains

the lower molecular weight compounds. This group of molecules

would have more edge valences to be satisfied, thus explaining the

additional bonds indicated in the extract.

18

the more significant portion of the plastic component, contains

the lower molecular weight compounds. This group of molecules

would have more edge valences to be satisfied, thus explaining the

additional bonds indicated in the extract.

IV. KINETIC STUDY OF THE FORMATION OF A

CHLOROFORM SOLUBLE MATERIAL

Theory

The following reaction mechanism is proposed for the

primary decomposition of a coal with fluid properties*

A P (1) P — SC + G^ 2)

This mechanism is similar to the mechanism proposed by Chermin and

van Krevelen^. A, represents the untreated coal; P. the plastic

stage; SC, the semi-coke and G]_, the low temperature gas products

from the primary decomposition*

In these tests chloroform extraction was used to determine

a value proportional to the amount of P produced* The relationship

between the plastic stage and the extract yield seems to be well

established by Dryden and Panchurst^ who showed that the residue does

not produce a fluid stage when the extract has been removed*

Procedure

The coal was heated in a pressure tight container as in

previous tests* In order to get reproducibility it was found that

19

IV. KINETIC STUDY OF THE FORMATION OF A

CHLOROFORM SOLUBLE MATERIAL

Theory

The following reaction mechanism is proposed for the

primary decomposition of a coal with fluid properties.

A --. P---

P (1) SC + G

I (2)

This mechanism is similar to the mechanism proposed b.Y Chermin and

van Krevelenl5• A, represents the untreated coal; P. the plastic

stage; SC, the semi-coke and~, the low temperature gas products

from the primary decomposition.

In these tests chloroform extraction was used to determine

a value proportional to the amount of P produced. The relationship

between the plastic stage and the extract yield seems to be well

established by Dryden and Panchurstl who showed that the residue does

not produce a fluid stage when the extract has been removed.

Procedure

The coal was heated in a pressure tight container as in

previous tests. In order to get reproducibility it was found that

19

20

the heating rate must be carefully controlled. Optimum characteristics

required of the heating process were a rapid rise in temperature to

the maximum temperature for the test and for maintenance of this tempera

ture for a time to produce the greatest extract yield. The rapid

temperature rise was important to minimize reactions before the

maximum temperature was reached and because a rapid temperature rise

usually accentuates the plastic stage and the coking properties of the

coal. It was desirable to hold the maximum temperature for a time

which would produce a maximum yield in order to relate one run to

another and to minimize the effect of errors. After some preliminary

tests the heating pattern that seemed most nearly to satisfy the

preceding conditions was a total heating time of 32 minutes, with the

temperature in the range of the last ten percent of the temperature rise

for approximately forty percent of the heating time. This system was

used for all the heating processes reported in this study.

After heating, the sample was extracted with chloroform and

evaporated as in the previous extraction tests. The yield of extract

was determined and a plot of yield versus temperature was made

(Figure 8). In this plot the temperature used was the mean temperature

for the final ten percent of the temperature rise.


Figure 6 shows a plot to determine the order of magnitude of the

activation energy of step 1 of the proposed model. This study utilized

the following relationships:

20

the heating rate must be carefully controlled. Optimum characteristics

required of the heating process were a rapid rise in temperature to

the maximum temperature for the test and for maintenance of this tempera

ture for a time to produce the greatest extract yield. The rapid

temperature rise was important to minimize reactions before the

maximum temperature was reached and because a rapid temperature rise

usually accentuates the plastic stage and the coking properties of the

coal. It was desirable to hold the maximum temperature for a time

loIhich would produce a maximum yield in order to relate one run to

another and to minimize the effect of errors. After some preliminary

tests the heating pattern that seemed most nearly to satisfy the

preceding conditions was a total heating time of 32 minutes, with the

temperature in the range of the last ten percent of the temperature rise

for approximately forty percent of the heating time. This system was

used for all the heating processes reported in this study.

After heating, the sample was extracted with chloroform and

evaporated as in the previous extraction tests. The yield of extract

was determined and a plot of yield versus temperature was made

(Figure 8). In this plot the temperature used was the mean temperature

for the final ten percent of the temperature rise.


Figure 6 shows a plot to determine the order of magnitude of the

activation energy of step 1 of the proposed model. This study utilized

the following rela t.ionships:

21

% yield- m kB Heating Time (constant)

-E/RT k = B 1

e

Therefore

ln.kB = ln( constant) J V R T

where k is the reaction rate constant, B and B-̂ are constants, E is

the activation energy for the step involved, R the gas constant and

T the absolute temperature in degrees K,

It follows that on a plot of the rate constant versus l/T

such as Figure °, the slope of the curve must represent E/R. In this

plot the low temperature range has the greatest significance since

it may be assumed that in this temperature range step 2 is negligible.

This plot indicates an activation energy for the initial step of 12 k

cal/mole and 20 k cal/mole for the second step assuming the second

step is controlling beyond the point of maximum yield*

It has been established by van Krevelen, van Heerden and

Huntjens^ that the activation energy for the primary gasification

(E2) is equal to approximately 5>0 k cal/mole for all coals* Chermin

and van Krevelen^ propose that unless E^ is approximately equal to

E2 the coal will not have a plastic stage which will contribute to a

satisfactory coke product* The value of E]_ and E2 determined by these

tests does not appear to agree with previously established values*

A plot similar to Figure 9 using the data of Dryden and Panchurst^

reveals activation energies of the same order of magnitude as for

this stud̂ r*

21

% yield • kB Heating Time (constant)

Therefore

-E/RT e

In.kB = In{constant) ~/RT

where k is the reaction rate constant, B and Bl are constants, E is

the activation energy for the step involved, R the gas constant and

T the absolute temperature in degrees K.

It follows that on a plot of the rate constant versus l/T

such as Figure 9, the slope of the curve must represent E/R. In this

plot the 1m., temperature range has the greatest significance since

it may be assumed that in this temperature range step 2 is negligible.

This plot indicates an activation energy for the initial step of 12 k

ca1/mole and 20 k cal/mole for the second step assuming the second

step is controlling beyond the point of maximum yield.

It has been established by van Kreve1en, van Reerden and

Huntjens14 that the activation energy for the primary gasification

(E2) is eq~l to approxilnate1y 50 k cal/mole for all coals. Chermin

and van Kreve1enlS propose that unless El is approximately equal to

E2 the coal 'Will not have a plastic stage which will contribute to a

satisfactory coke product. The value of El and E2 determined b.1 these

tests does not appear to agree with previously established values.

A plot similar to figure 9 using the data of Dryden and Panchurstl

reveals activation energies of the same order of magnitude as for

this study.

22

Some observations of the physical properties of the coal as

it was removed from the heating process deserve some mention here*

The heated coal appeared much the same as before heating (rather

finely ground) up to the point of maximum yield. At or near the

point of maximum yield the coal sample was caked but not swelled.

Higher temperatures produced a swelled sample with a relatively high

swelling index.

22

Some observations of the physical properties of the coal as

it was removed from the heating process dese~ some mention here.

The heated coal appeared IlRlch the same as before heating (rather

finely ground) up to the point of maximum yield. At or near the

point of maximum yield the coal sample was caked but not swelled.

Higher temperatures produced a swelled sample 'With a relatively high

swelling index.

V. CONCLUSIONS

The use of the infrared spectrophotometry and the extraction

techniques have indicated the following information regarding the

primary decomposition of the coal.

1. The heated coal and the chloroform extract show appreciable

increases in the molecular OH bonds*

2© The chloroform extract yield shows a higher hydrocarbon

content than' the untreated coal. This is particularly significant

since extraction was after heating to temperatures at which some

hydrocarbons leave the material as a gas. The extract must consist

of the lower molecular weight portions of the plastic material of

the coal* This reasoning would imply that the extract is composed

of smaller numbered carbon ring compounds with a large number of

hydrocarbon edge groups.

3o Both the extract and the heated coal show marked changes

in the carbonyl and ether absorbtion region. The results of this

study alon& are not sufficient to discuss these changes except in a

general way. It appears that there is a shift from the carbonyl

bonds toward ether bonds as the coal is heated. A mechanism may be

proposed which includes this change and the increase in the molecular

OH bonds«

k» The extract shows absorbtion at four or more bands for

which there, is no absorbtion in the untreated coal. These absorbtions

23

V. CONCLUSIONS

The use of the infrared spectrophotometry and the extraction

techniques have indicated the following information regarding the

primary decomposition of the coal.

1. The heated coal and the chloroform extract show appreciable

increases in the molecular OR bonds.

20 The chloroform extract yield shows a higher hydrocarbon

content than' the untreated coal. This is particularly significant

since extraction was after heating to temperatures at which same

hydrocarbons leave the material as a gas. The el...-tract must consist

of the lowe~ molecular weight portions of the plastic material of

the coal. This reasoning would imply that the extract is composed

of smaller numbered carbon ring compounds with a large number of

hydrocarbon edge groups.

30 Both the extract and the heated coal show marked changes

in the carbonyl and ether absorbtion region. The results of this

stuqy alon& are not sufficient to discuss these cha-~ges except in a

general way. It appears that there is a shift from the carbonyl

bonds toward ether bonds as the coal is heated. A mechanism may be

proposed which includes this change and the increase in the molecular

OR bonds.

4. The extract shows absorbtion at four or more bands for

which there .. is no absorbtion in the untreated coal. These absorbtions

23

2U

appear to substantiate the belief that there are increased molecular

OH bonds in the heated coalo

There is an eventual disappearance of all or almost all of

the bonds except the C-C bonds as the coal is heated to the coking

temperatures* The final product has a graphitic structure -with the

more fluid coals showing a larger crystallite size.

6* A kinetic study of the initial reaction which results in

a plastic state for the coal indicates activation energies for of

approximately 12 k cal/mole for the first step of the decomposition

process and 20 k cal/mole for the second step of the proposed

mechanism.

It is the author's opinion that the conclusions which may be

drawn from the results of these tests are less important than the

direction of study of which they seem to point. As newer techniques

such as these are developed and as more data become available from

these techniques, a more specific understanding of the primary decom

position of coal will be possible. A good understanding of the

activation energies of the primary decomposition of the coals involved

could change the blending of coals to produce good coke from its

present empirical stage to a much more exact science*

24

appear to substantiate the belief that there are increased molecular

OH bonds in the heated coalo

5. There is an eventual disappearance of all or almost all of

the bonds except the C-C bonds as the coal is heated to the coking

temperatures. The final product has a graphitic structure with the

more fluid coals showing a larger crystallite size.

6. A kinetic study' of the initial reaction which results in

a plastic state for the coal indicates activation energies for of

approximately 12 k cal/mole for the first step of the decomposition

process and 20 k cal/mole for the second step of the proposed

mechanism.

It is the author's opinion that the conclusions which may be

drawn from the results of these tests are less important than the

direction of study of which they seem to point. As newer techniques

such as these are developed and as more data become available from

these techniques, a more specific understanding of the primary decom

position of coal will be possible. A good understanding of the

activation energies of the primary decomposition of the coals involved

could change the blending of coals to produce good coke from its

present empirical stage to a much more exact science.

VI. RECOMMENDATIONS

The studies presented in this report represent only a

beginning in the use of the techniques described to study the primary

decomposition of coal. Infrared absorbtion bands must be more positively

identified, particularly those for the extract yields, for a fuller

understanding of the data obtained by this technique and more data is

necessary for a more thorough kinetic study.

For a better identification of the spectral bands in the

extract, a fractional distillation might be helpful. Gas chromotography

and mass spectrometry could be used to identify the lighter fractions

of the extract.

The fdata which are necessary for a good kinetic study must

include the extract yield as a function of temperature which was

determined in this study and also the extract yield as a function of

time as a constant temperature. Since the plastic stage represented

by the extract yield is decomposing as well as forming, the amount of

the decomposition or weight change of the sample must be obtained also.

The author plans to obtain these required data by the use of vertical

furnace in which weight changes may be recorded as a function of time.

A much more thorough kinetic study should be possible when the

additional data are available.

25

VI. RECOMMENDATIONS

The studies presented in this report represent only a

beginning in the use of the techniques described to study the primary

decomposition of coal. Infrared absorbtion bands must be more positively

identified, particularly those for the extract yields, for a fuller

understanding of the data obtained by this technique and more data is

necessar,y for a more thorough kinetic study.

For a better identification of the spectral bands in the

extract, a fractional distillation might be helpful. Gas chromotography

and mass spectrometry could be used to identify the lighter fractions

of the extract.

The ~da.ta which are necessary for a good kinetic study must

include the extract yield as a function of temperature which was

determined in this study and also the extract yield as a function of

time as a oonstant temperature. Since the plastic stage represented

by the extract yield is decomposing as well as fOrming, the amount of

the decomposition or weight change of the sample must be obtained also.

'ilie author plans to obtain these required data by the use of vertical

furnace in which weight changes may be recorded as a function of time.

A much more thorough kinetic study should be possible when the

additionai data are available.

2.5

APPENDICES APPEmllCES

•Figure 1.

'li. ! I

'i i "1-,· ~ I~: , ,

'j : I ~', i

'I . . , .,

, !

I:

" , '.J : __

If : ~ -; i

I c" . ~ j 0.1 r

.. ,t . j ,J I

0'" 0 .•

.. ll. o. I I ,I. In~ !i' I 0.' 1 i 0.7

loc. 0.8,

0 00' 0 1.0 ~ I .C C.O

I,.~ .! I: I r I.lI I ! II~

W!LVELENGTH IN MICRONS

;Figure 1. DIfferential iDfrared spectrophotometric paltern. Untreated coal In the reference beam; coal beated to the aqfte,/llDJ range In the sample beam.

: I ~ \ 1 .~ r j ! i ~

0.'

0.-

WAVELENGTH IN MICRONS

Figure 2. Differential infrared spectrophotometric pattern to prove technique. Untreated coal from the same sample in both the reference and sample beams.

/

lill mil " .

I' i

Iii

'.. '. ; I' " , .' 1 .1 ,T

I L: i I.: i I 'I II I

II' ,

: I ['

I i

, : ~. .[ ! ;

WAVELENGTH IN MICRON!!

Figure 2. DltferentlallDfrare<l 'spectrophotometric p-artern to prove technique. Untreated coal from tbe same sample in both tba reierence and sample beams.

1

,I

, 'I

: I I

·1 I'

'"I'

I'\) co

Figure 3. Infrared spectrophotometry pattern of coals heated in a closed crucible.

29

2.1 5 4 6 7. 7.5 10

---0 - Furnace at SOOOF, coal sample 1 gram -··-u - In furnace 2 mln~a -·-1 - In furnace 1 minutes ---m - In furnace 3 Dllnutea

- IV - In furnace 5 minutes (max. coal temperature approXimately 4'15"C.

Figure 3. Infrared spectropllotometrlc pattern of coals beated In a closed crucible.

Figure 5. Chloroform extract yield vs. blank,

! !

IJ ~I:

I'

. !

, ",~ ",~

j :

Figure 4. Untreated coal vs. potassium iodide blank ,

1 ' ;

, , ,

.j '

'1"

, ' i

-~: , ~~~~~~~~~ , i

,"

Figure 5. Chloroform extract yield vs. blank.

w o

Figure 7 Extract residue vs. potassium iodide blank

~ . "'I'? , ~ .'.1'" ,~ '?' ': .. " ,,~ . '~ '1" '1" , lIHf " . ':.' : i I I ~ i ' I i II

, Ii, i \,,! _Zl ! I ! , I i I

I I!i: I~i \11 ! :'1

,

I I I I

I . I

. , ! I rl~ ; ,~ I I ! I I I I I i 'I

i II ! I I I II [ I I I I

i I

;' ! I

. , II : I. ! I i ,

!

I I I' I i' 1

,I . I I! I . i I I ,

flml± ! ,

I

mm· I I i II I: I . ! i! ! i

Iffffifi ' . , ... , ,

Figure 6 _. Untreated coal reference beam. Chloroform extract yield sample beam ....

" "I" .. "'. . ~ ."i" . " .:'1". " 'i". ".m "i". '1" ."1" '1" '1" ,

i ~ [ •

,

I . i •

, I , , ,

I

, I

i' I i I . ,

; ; , I I ,

i ,

i , !

, II I ! i , I' , i: ,

! I , , , ,

; I : , , , , ,

, , :

L : , I

. , I ,

, I ,

~ , . I

! I, rIl , . . , .

, , ,

• i , , ,

• i I i I ! II i I ii, I I I ! . i , , '

Ie , . ......

Figure 7.. Extract residue vs. potassium iodide blank.

32

T 1 1 1 1 1 r

200 240 280 320 360 400 440 480 520 T E M P E R A T U R E ° C

Figure 8. Chloroform extraction yield v s . temperature .

31 1 1 1 ' 1 1 1 r

Figure 9. Ln. % extract ion y ie ld v s . 1/T to determine activation e n e r g i e s .

0 ...J UJ

~

z 0 ~ t.)

~ It: ~ )(

UJ

~ °

o

6

5

4

3

2

.5

200

32

520 TEMPERATURE °c

Fi~ure 8. Chloroform ,.'xtractioJ1 :'iield \'5. lenlj)erature.

3.--------.--------.--------r--------~------~--------~-----,

~ 2 ~

~ t.)

ct a: .... ~

Z ...J

1.3

keol Et - 20 mole

o

1.4 1.5 1.7

keol = 12.4 mole

o

1.8

Figure 9. Ln. % extraction yield vs. liT to determine activation energies.

1.9

BIBLIOGRAPHY

1 I.G.C. Dryden and K.X. Panchurst, Fuels, 3U 363, July (1955)

2 M.M. Stimson and M.J. O'Donnell, Jour. Am Chem Soc 7k 1805 (1952)

3 U. Schiedt and H. Reinwein, Z. Naturforsch 76, 270 (1952)

k U. Scheldt, Ibid, 86, 16 (1953)

5 R. A. Friedel and J. A. Queiser, Anal. Chem* 28 No. 1 , 22, Jan. (1956) —

6 J. K. Brown, Chem Soc. Journal of Inst, of Fuels, 28 218, May (1955) —

7 J. K. Brown, and P. B. Hirsch, Nature 175 , Ebr. 5, 229 (1955)

8 J. K.-Brown, Chem. Soc. Journal, pp. 752-757, Jan.-Mar. (1955)

9 Fuels and Combustion Handbook, Johnson and Auth, 1 s t , Edition, McGraw-Hill, New York, (1951)

10 Chemistry of Coal Utilization, Vol. I, John Wiley, (19^5)

1 1 H. H. Storch, Jour, of Inst, of Fuels, 28 151*, April (1955)

12 A. Whitaker, Jour, of Inst, of Fuels, 28 218, May (1955)

13 D. Fitzgerald, Fuel, J35 178 April (1956)

lU D. W. van Krevelen, C# van Heerden and F. J. Huntjens, Fuel, 30 253, (1951)

15 H. A. G. Chermin and D. W. van Krevelen, Fuel, 36 85, Jan. (1957)

16 W. A. KLnkby, J. R. A. Lakey and E. J. Sargent, Fuels, 33, 1*80. (195U)

33

BIBLIOGRAPHY

1 IoG.Co Dryden and K.X. Panchurst, Fuels, 34 363, July (1955)

2 MoM. stimson and M.J. O'Donnell, Jour. Am Chern Soc. 74 1805 (1952) --

3 U. Schiedt and H. Reinwein, Z. Naturforsch 76, 270 (1952)

4 U. Scheidt, Ibid, 86, 16 (1953)

5 R. A. Friedel and J. A. Queiser, Anal. Chem. 28 No.1, 22, Jan. (1956)

6 J. K. Brown, Chern Soc. Journal of Inst. of'Fuels, 28 218, May (1955)

7 J. K. Brown, and P. B. Hirsch, Nature 175, Ebr. 5, 229 (1955)

8 J. K. -'Brown, Chern. Soc. Journal, pp. 752-757, Jano-¥...ar. (1955)

9 Fuels and Combustion Handbook, Johnson and Auth, 1st. Edition, McGraw-Hill, New York, (1951)

10 Chemistry of Coal Utilization, Vol. I, John Wiley, (1945)

11 H. H. Storch, Jour. of Inst. of Fuels, ~ 154, April (1955)

12 A. Whitaker, Jour. of Inst. of Fuels, 28 218, May (1955)

13 D. Fitzgerald, Fuel, ~ 178 April (1956)

14 D. W. 'van Krevelen, C. van Heerden and F. J. Huntjens, Fuel, .lQ. 253, (1951)

15 H. A. G. Chermin and D. W. van Krevelen, Fuel, .36 85, Jan. (1957)

16 W. A. Kinkby, J. R. A. Lakey and R. J. Sargent, Fuels, ll, 480, (1954)

33



by


An abstract of a thesis submitted to the faculty of the University of Utah in partial fulfillment of the requirements for the degree of

Master of Science

Approved by the faculty committee in

August, 1957

Dr. George Richard Hill, Chairman, Supervisory Committee


University of Utah 1957



by

Raymond Virgil Sm:i. th

An abstract of a thesis submitted to the faculty of the University of Utah in partial fulfillment of the requirements for the degree of

Master of Science

Approved by the faculty committee in

August, 1957

Dr. George Richard Hill, Chairman, Supervisory Committee


Uni versi ty of Utah 1957

ABSTRACT

For the differential I-R technique described in this paper,



received from the mine and this was placed in the reference beam.





infrared range.


temperatures in the plastic range and then extracted with chloroform.







the coal!s primary decomposition. Activation energies thus obtained


general order of magnitude of 20 to 30 k.cal/mole*

ii

ABSTRACT

For the differential I-R technique described in this paper"



recei ved from the mine and this was placed in the reference beam.





infrared range.


temperatures in the plastic range and. then extracted with chloroform.







the coal r s primary de compo si tion. Activation energies thus obtained


general order of magnitude of 20 to 30 k.cal/mole.

i1

study of the primary decomposition of coal by infrared

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